1. Field of the Invention
The present invention relates to a wheeled vehicle and, more particularly, to a castor for a cart, chair and the like.
2. Description of the Related Art
A conventional castor in accordance with the prior art shown in FIGS. 1 and 2 comprises a fixed tube 11, a castor body 12 swivelably mounted on the fixed tube 11 and having an interior provided with a retaining hole 121, a first engaging member 122 mounted on the castor body 12, a control rod 113 movably mounted in the fixed tube 11 and extended through the castor body 12, a bushing 114 mounted between the fixed tube 11, the castor body 12 and the control rod 113, a second engaging member 1141 mounted on a mediate of the control rod 113, a roll 1131 mounted on a top of the control rod 113, a retaining block 116 mounted on a lower end of the control rod 113, a push block 1132 mounted on a bottom of the control rod 113, a cam 112 rotatably mounted in the fixed tube 11 and having a periphery provided with a first ear 1121 and a second ear 1122 which are movable to press the roll 1131, an operation handle 111 extended through the cam 112 to rotate the cam 112, two rollers 13 rotatably mounted on two opposite sides of the castor body 12 and each having a side provided with a plurality of locking grooves 131, an elastic unit 115 mounted between the control rod 113, the bushing 114, the second engaging member 1141 and the retaining block 116 to provide a restoring effect to the control rod 113, and a braking unit 117 mounted on the castor body 12. The braking unit 117 includes a slide 1172 movably mounted on the castor body 12 and a braking rod 1171 connected with the slide 1172. The slide 1172 has a side provided with a ramp 1173 aligning with the push block 1132.
In operation, when the cam 112 is rotated by the operation handle 111 in a first direction, the first ear 1121 of the cam 112 is movable to press the roll 1131 as shown in FIG. 2. In such a manner, the roll 1131 is moved downward to press and move the control rod 113 which moves the retaining block 116 so that the retaining block 116 is extended into and locked in the retaining hole 121 of the castor body 12 to lock the castor body 12. Thus, the castor body 12 is locked by the control rod 113 and cannot be rotated relative to the fixed tube 11, while each of the rollers 13 can be rotated relative to the castor body 12 freely, so that the castor is moved linearly and cannot be turned around.
Alternatively, when the cam 112 is rotated by the operation handle 111 in a second direction, the second ear 1122 of the cam 112 is movable to press the roll 1131. In such a manner, the roll 1131 is further moved downward to press and move the control rod 113 which moves the second engaging member 1141 so that the second engaging member 1141 is moved to engage the first engaging member 122 to lock the castor body 12. Thus, the castor body 12 is locked by the control rod 113 and cannot be rotated relative to the fixed tube 11. At the same time, when the control rod 113 is moved downward, the push block 1132 is moved by the control rod 113 to abut the ramp 1173 of the slide 1172, so that the slide 1172 is pushed to move the braking rod 1171. In such a manner, the braking rod 1171 is extended into and locked in one of the locking grooves 131 of each of the rollers 13 so as to lock each of the rollers 13. In such a manner, each of the two rollers 13 is locked by the braking rod 1171 and cannot be rotated relative to the castor body 12. Thus, the castor is braked to stop moving and cannot be turned around.